The present invention relates to a pressure regulating solenoid operated hydraulic valve.
In certain applications, for example for actuation of a clutch in an agricultural or industrial tractor, a hydraulic valve is required that can deliver a regulated pressure in response to an applied electrical control signal. For this purpose, hydraulic valves are known that have a valve spool slidably mounted within a housing. The spool has lands that cooperate with ports in the housing to vary the flow between a pressure supply line, a line leading to the load to be supplied and a return line to a reservoir or tank. One end of the spool is acted upon by the pressure in a control chamber and the other is acted upon in the opposite direction by a spring. The position of the spool in the housing can therefore be set by varying the pressure in the control chamber and this in return regulates the pressure supplied to the load.
The control chamber of the spool valve is permanently connected to a pressure source and is also connected to the return line by way of a solenoid operated valve. The latter valve comprises a ball urged against a valve seat by the armature of a control solenoid of the spool valve. The greater the current flowing through the solenoid, the greater is the force applied by the armature to urge the ball against its seat and therefore the greater is the pressure in the control chamber. Thus force exerted by the solenoid determines the pressure in the control chamber, this in turn determines the position of the valve spool in the housing and therefore the pressure of the hydraulic fluid supplied to the load.